As shown in FIG. 15, a conventional magneto-optical disk A includes a multiple of lands and grooves for recording data. The lands and grooves are conceptually divided circumferentially of the disk at a predetermined angle into a number of address-assignable sectors. Further, the magneto-optical disk A is conceptually divided by physical formatting into zones each including a series of sectors. The number of zones depends on the capacity and kind of the magneto-optical disk. For example, the magneto-optical disk of a 640 MB capacity is divided into eleven zones, whereas the magneto-optical disk of a 1.3 GB capacity is divided into eighteen zones as shown in FIG. 16. The lands, grooves and sectors are not illustrated in the accompanying drawings. In practical application the lands and grooves often have a spiral form.
Each of the zones in the magneto-optical disk A is given logical addresses at the time of physical formatting. The logical addresses are assigned in order from the radially inward through the outward side or the other way round, i.e. from the radially outward through the inward side, of the magneto-optical disk A according to industrial standards. For example, in the magneto-optical disks of 230 MB, 540 MB and 640 MB capacities, the logical addresses are assigned from the radially most inward zone through the most outward zone. On the other hand, in the magneto-optical disks of 1.3 GB capacity, as shown in FIG. 16, the logical addresses are assigned from the radially most outward zone through the most inward zone. As described, the order in which the logical address assignment is made is an industrial standard set forth for each kind and capacity of the magneto-optical disks, and therefore cannot be altered arbitrarily.
Next, description will be made for a series of procedures executed when a command is received from a host C for writing data onto a magneto-optical disk A. When loaded with a magneto-optical disk A, the recorder/player B in FIG. 15 calls up a medium type identifier 100 to read medium management information A1 which is pre-recorded on the magneto-optical disk A, and identifies the type of the disk.
An address converter 110 makes reference to a medium management table 120, reads data about the order of logical address assignment which is the standard set forth for each type of the disks, and based on this data obtains the order of the logical address for each zone. For example, if the magneto-optical disk is of the 230 MB, 540 MB or 640 MB capacity, the address converter 110 recognizes that the logical addresses are assigned from the radially most inward zone through the most outward zone. On the other hand, if the magneto-optical disk is of the 1.3 GB capacity, the address converter 110 recognizes that the logical addresses are assigned from the radially most outward zone through the most inward zone.
Further, the address converter 110, upon reception of logical addresses specified by the host C, makes reference to the medium management table 120, reads data about the number of sectors in each zone which is a standard set forth for each type of the disks, and obtains preliminary physical addresses based on the read data. These preliminary physical addresses will be formal addresses if there is no defective sector found in any zones of the magneto-optical disk A, or if defective sectors are found to have no influence on the address assignment during the obtainment of the physical addresses. The address converter 110 makes reference to PDL (Primary Defect List, to be described later) and SDL (Secondary Defect List, to be described later) contained in the medium management information A1, and checks if there will be an influence on the preliminary physical addresses.
Here, comparison is made between FIG. 18 and FIG. 19: when a defective sector is detected in a zone during the physical formatting of a magneto-optical disk A, the defective sector is skipped by the step of writing initializing data, and this zone which includes the defective sector is extended into a spare zone in order to provide a predetermined number of flawless sectors by using a spare sector available in the spare zone. The physical address of the defective sector is recorded in the medium management information A1 for management of the medium. Such a defect, i.e. a defect in which a logical address can be assigned while skipping defective sectors, is referred to as a primary defect. A set of addresses of the defective sectors that fall into the category of the primary defect is called PDL.
On the other hand, compare FIG. 18 and FIG. 20: when a defective sector is detected in a zone while writing data, the data is written onto another sector in the spare zone, in place of the defective sector. Then, the physical address of the defective sector and the physical address of the spare sector which replaced the defective sector are recorded onto the medium management information A1 for the sake of address conversion. Such a defect, i.e. a defect in which a replacing spare sector can be specified by address conversion, is called secondary defect. A set of addresses of the defective sectors that fall into the category of the secondary defect is called SDL.
Specifically, when a magneto-optical disk A includes primary defects, the address converter 110 makes reference to the PDL, shifts a given address according to the number of the primary defects, and thereby obtain a correct physical address. On the other hand, when there are secondary defects, and their preliminary physical addresses are included in the SDL, the address converter 110 makes reference to the SDL, and thereby obtain physical addresses of replacing sectors. Thus, the address converter 110 converts logical addresses given by the host C into correct physical addresses.
With the above, data sent from the host C together with specifying addresses are temporarily stored in an unillustrated data buffer provided in the recorder/player B. A data reading/writing section 140 writes the data according to the physical addresses obtained by the address converter 110. When the writing of data is complete, the data reading/writing section 140 reports the completion of the operation to the host C. Such data writing is performed for the number of blocks specified by the host C.
Next, description will be made about access to a magneto-optical disk A. Generally, the host C, operating on the basis of an OS (Operating System) which provides file managing capabilities, controls the location of files stored on the magneto-optical disk A via the recorder/player B. For this purpose, file management information A2 which indicates file location is stored at a head portion of the zones assigned with logical addresses on the magneto-optical disk A. Whenever a file is read, made, updated or deleted on the magneto-optical disk A, reference is made to the file management information A2 and the information is updated. Therefore, the head portion of the zones on the magneto-optical disk A is the area that is accessed most frequently.
When files are added to the magneto-optical disk A, writing of file data is made in an ascending order of logical addresses, i.e. from a zone having relatively small logical addresses through a zone having relatively large logical addresses. For example, in magneto-optical disks of the 230 MB, 540 MB and 640 MB capacities, the logical address assignment is made from the radially most inward zone through the most outward zone, and thus the file data is written from the inward toward the outward side. On the contrary, in magneto-optical disks of the 1.3 GB capacity, as shown in FIG. 16, the logical address is assigned from the radially most outward zone through the most inward zone, and thus the file data is written from the outward to the inward side.
As will be understood, in a magneto-optical disk A, it is very rare that each zone is accessed equally, and it is very usual that access is concentrated on zones having the smallest logical addresses, in reading/writing of data.
Next, description will be made about an operation for physically formatting a magneto-optical disk A. When loaded with a magneto-optical disk A, the recorder/player B calls up the medium type identifier 100 to read medium management information A1 which is pre-recorded on the magneto-optical disk A, and identifies the type of the disk. When the physical formatting is requested from the host C to the recorder/player B, the address converter 110 makes reference to the medium management table 120, reads data about the order of logical address assignment which is a standard set forth for each type of the disks, as well as the first and the last physical addresses for each zone based on the read data, and obtains a physical address for each zone.
A physical formatter 130 writes initializing data, within the range from the first through the last addresses obtained for each zone, in the order from a zone having the smallest logical address through a zone having the largest logical address. When there is a failure in writing the initializing data, a recovery section 150 makes are try regarding the writing of the initializing data until a predetermined number of retries is reached. If the writing is not successful within the predetermined number of retries, this sector is treated as defective, and the physical address of the defective sector is tentatively stored in the form of PDL in a memory 160. This formatting procedure is executed to all sectors in all zones which are to be initialized.
When the number of defective sectors detected during the formatting procedure has exceeded a predetermined limit, the physical formatter 130 cancels the formatting procedure and reports a disk error to the host C. On the other hand, when the number of defective sectors did not exceed the limit, the physical formatter 130 copies the PDL, which has been stored in the memory 160 during the formatting, onto the medium management information A1 on the magneto-optical disk A, and reports a successful completion of the formatting to the host C. The above is a conventional physical formatting procedure.
Now, consider a case in which the host C sends a data writing command accompanied with address specification in the form of logical address. The address converter 110 converts the given logical address into a physical address, obtains physical addresses of the first and the last sectors onto which the data is to be written, and further, checks if there is any defective sectors within the range specified by the addresses. If there is no defective sector within the range, each of necessary steps such as erasing/writing/verifying procedures is performed one time to every sector, continuously from the first to the last sectors specified by the addresses for the data writing.
However, if there are defective sectors within the specified range, the data writing must be made while skipping these defective sectors. Therefore, the erasing/writing/verifying procedures are repeated as many times as the number of regions fragmented by the defected sectors. In other words, each of the erasing/writing/verifying procedures is performed to the plurality of regions, at a cost of idling rotations of the magneto-optical disk A, resulting in a prolonged data writing time.
Likewise, consider a case in which the host C sends a data reading command accompanied with address specification in the form of logical address. The address converter 110 converts the given logical address into a physical address, obtains physical addresses of the first and the last sectors from which the data is to be read, and further, checks if there is any defective sectors within the range specified by the addresses. If there is no defective sector within the range, a reading procedures is performed one time, continuously from the first to the last sectors specified by the addresses for the data reading.
However, if there are defective sectors within the specified range, the data reading must be made while skipping these defective sectors. Therefore, the reading procedure is repeated as many times as the number of regions fragmented by the defected sectors. In other words, the reading procedure is performed to the plurality of regions, at a cost of idling rotations of the magneto-optical disk A, resulting in a prolonged data reading time.
With the above, as described earlier, there is the file management information A2 at a zone that has the smallest logical address, and whenever a file is read or written, reference is made to the file management information A2 and the information is updated. Therefore, access is concentrated on the zone having the smallest logical address. If this zone contains many defective sectors, a long time must be spent for updating the file management information A2 every time the host C requests file writing or reading, and this results in delayed response to the host C.
There is another problem: whenever a file is accessed for reading or writing, the address converter 110 searches the PDL and the SDL in the medium management information A1 in order to convert logical addresses specified by the host C into physical addresses. This search is executed on the basis of an unillustrated control program stored in the recorder/player B. The PDL lists a number of sectors for which address shifting is necessary, whereas the SDL contains physical addresses of replacement sectors. Obviously therefore, a long time must be spent for the search if there are many defective sectors, since the PDL and the SDL contain many addresses.
The prolonged search time spent by the control program results in extra waiting time due to disk idling rotations. Especially, according to a recent recorder/player B which features a high-speed disk rotation, an amount of time necessary for the disk to make a single turn is shorter than an amount of time necessary for searching the PDL or the SDL. As a result, performance decrease is apparent when using the recorder/player B.
There is still another problem. Specifically, when the host C requests the recorder/player B to read or write data, and if there is a failure in the reading/writing, the recovery section 150 performs a retry with regard to the data reading/writing. When this retry is successful and therefore the reading/writing is completed, as compared to a case where there is no failure in the procedure, the amount of time needed for the procedure is longer by the amount of time spent for the retry procedure. Due to increased capacity, magneto-optical disks A in recent years have an increasingly narrow track pitch. This has increased probability of executing the retry procedure and there is a tendency that the number of retries is increasing. As a result, the amount of time spent for the retries and the number of retries have a significant influence on the performance of the recorder/player B.
As described, it is known that the zone having the smallest logical address is accessed very frequently since it includes the file management information A2. A large number of retries performed in this zone poses a problem of delayed response to the host C after the host C sends a writing command or a reading command.
Further, in a magneto-optical disk A in which logical addresses are assigned alternately to the land and the groove, there is usually no problem in reading/writing data whether the first logical address is given to a land or a groove. However, according to the conventional magneto-optical disk A, the zone having the smallest logical address is unchangeably fixed to either one of the land and the groove.
Assume a situation, for example, in which there are more defective sectors in the lands than in the grooves. If it is possible to change so that logical address assignment is started from the grooves, then it becomes possible to speed up access during the referencing and updating of the file management information A2. However, if the zone which has the smallest logical address is unchangeably provided by the lands due to the standard, it has not been possible to improve on the access time by reducing access time for the referencing and updating of the file management information A2.
In addition, although the magneto-optical disk A tends to have a larger capacity, it can be said that users rarely use up all of the capacity, and in great majority of cases only a portion of the entire capacity is used. Even under such a situation where use of the capacity by the users is limited, the current physical formatting procedure provides formatting for the entire capacity. This has created a problem that, for example, as long as 18 minutes have to be spent for physically formatting a 1.3 GB magneto-optical disk for its entire capacity, resulting in an inconvenience to the users.